@tap82: That has nothing to do with hacks, and everything to do with how you sideload your books.
TL;DR (because it's been covered to death already): Calibre does the right thing by default.
Amazon's email delivery service is tied to the personal document service/cloud, which, obviously, delivers personal documents ;p.
And before you ask, no, tricking the framework into believing personal documents are really books is out of the question. (JBPatch used to be able to workaround some aspects of that, but never entirely, and that was seventy billion firmware versions ago).
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